Network sharing

ABSTRACT

A wireless communication system includes one or more base stations able to divide resources between multiple network operators sharing the base station. A shared base station is configured to monitor a contribution to the load on the base station associated with network operators sharing the base station resources and to provide the determined contribution to the load to one or more other base stations for use in load balancing between the base stations.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/119,061 filed Nov. 20, 2013, which is a 371 of internationalPCT/JP2012/061930, filed May 1, 2012; which claims the benefit ofpriority from United Kingdom patent application number 1108525.5, filedon May 20, 2011, the contents of which are incorporated herein in theirentireties.

TECHNICAL FIELD

The present invention relates to a radio access network in a cellular orwireless telecommunications network, and particularly but notexclusively to sharing the radio access network between multipleoperators. The invention has particular but not exclusive relevance towireless telecommunications networks implemented according to the LTEstandard.

BACKGROUND ART

Radio Access Network (RAN) sharing deployment scenarios are known andmethods and abilities to facilitate implementations of these scenarioshave been introduced into the 3G standards since Release 5.

RAN sharing provides a way for network operators (service providers) toreduce their capital expenditure requirements and/or widen the areacovered by a cellular communication service when setting up a wirelesscommunications network. Rather than each operator having to providetheir own base station and associated equipment for each cell of thenetwork, an operator sharing the RAN of another operator is able toprovide their service into areas served by the other operator withouthaving to invest in their own base stations in that location.

Furthermore, by reducing the number of base stations that must beprovided and operated, the ongoing operating costs can be reduced forthe sharing operators. Indeed, each base station may draw a large amountof electricity during operation, and therefore reducing the number ofoperating base stations may significantly reduce electrical powerrequirements and may therefore also be considered environmentallyfriendly.

Typically, sharing of RANs by operators has been a symmetric arrangementin which each operator gets some access to the RAN of the otheroperator. In the extreme, such an arrangement allows two operators toprovide service to the same area with half as many base stations (andtherefore with significantly reduced cost) as would be required if nosharing was possible.

RAN sharing is particularly advantageous in areas in which an operatorhas cell capacity that is underused, as this spare capacity can then beshared with no impact on the original operator's ongoing serviceprovision. Furthermore, RAN sharing may be useful in order to ensurethat a service provided by an operator is able to reach a certainpercentage of the population, which may be specified by licenseconditions in some countries, without requiring each operator to installexpensive capacity in remote areas in which it is likely to beunderutilized.

Currently, the standards relating to RAN sharing are limited to twoscenarios. In a first scenario, only the RAN base stations themselvesare shared by the different operators. In a second scenario, parts ofthe core network, for example the Evolved Packet Core (EPC) in LTE, canbe shared as well as the RAN base stations, further decreasing capitalexpenditure costs in setting up the network. In each case, sharing ofthe RAN can be arranged to use split frequencies, in which each operatorsharing the RAN has allocated (different) frequency ranges, or may usecommon frequencies in which the full range of frequencies is availablefor use by either operator.

The mechanisms for sharing of RANs may also be useful in the case ofmergers of operator companies, allowing the two operators to merge theirnetwork services without any significant interruptions in serviceprovision.

To date, it has always been the case that the network provider thatmakes the RAN available for sharing has been one of the serviceproviders, or operators, sharing the network. However, the inventorshave realised that in future this may not always be the case. Inparticular, in some cases it is possible that a specialist networkprovider may install network capacity that can then be used by unrelatedservice providers.

The recent economic situation has provided further impetus for networkoperators to reduce costs, and therefore increased the trend to sharenetworks with other operators. In particularly, network operators areincreasingly considering the scenario in which the owner of the networkis not themselves a service provider. In this case, each serviceprovider, or operator, will purchase a share in the capacity of thenetwork. This may be based on their respective holding of frequencylicenses in the relevant spectrum.

The first arrangement in which a number of network operators will relyon a third party network provider to provide a shared access network hasnow been proposed. However, there remain a number of issues to beaddressed in the standards to enable this scenario of RAN sharing to beimplemented.

For example, in order to enable this new RAN sharing scenario, it isimportant that the standard provides ways to guarantee fair usage of thenetwork resources by each of the network operators according to theirshare in the RAN. Each network operator must be able to monitor thenetwork performance to ensure that service level agreements are met andto identify any potential problems. Furthermore, each network operatormust be able to operate their share of the network in a way thatprovides complete access to all existing features defined in thestandards.

The ability for network operators sharing capacity in a communicationnetwork to monitor the network performance in a shared RAN is alsouseful in enforcing sharing agreements when one of the operators is alsothe owner of the shared RAN and/or when the network operators areassigned different proportions of the network resources (i.e. unequalshares).

SUMMARY

Embodiments of the invention aim to at least partially address some ofthe problems with the prior art described above.

According to an aspect of the invention, there is provided a basestation operable to share resources between at least two networkoperators, the base station comprising means for determining acontribution to a load on the base station associated with a one of thenetwork operators, and means for providing the determined contributionto the load on the base station associated with the one network operatorto a further base station for use in load balancing between the basestations.

The network operators may operate independent Public Land MobileNetworks (PLMN) and be associated with a unique PLMN id value used toidentify a respective PLMN.

The base station may further comprise means for receiving from thefurther base station contributions to the load on the further basestation associated with each network operator.

The base station may further comprise means for determining if thecontribution to the load for the one network operator is above athreshold load for that network operator, and means operable, inresponse to determining that the contribution to load is above thethreshold level for that network operator, to cause at least oneconnection associated with the one service provider to be handed over tothe further base station. The means operable to cause at least oneconnection to be handed over may only do so if such a handover does notoverload the further base station. The base station may further comprisemeans for communicating an available capacity associated with eachnetwork operator on the base station to the further base station.

According to a further aspect of the invention, there is provided a basestation operable to share resources between at least two networkoperators, the base station comprising means for receiving a messagefrom a further base station, the message comprising information relatingto a contribution to a load on the further base station associated witha one of the network operators, and means for performing load balancingbetween the base station and the further base station based on thereceived information.

The means for performing load balancing may be configured to adjust ahandover trigger level associated with the one network operator, thehandover trigger level being used to control handover of connectionsassociated with the one network operator between the base station andthe further base station. The means for receiving may comprise an X2network interface for communication using the X2 interface between basestations.

According to a further aspect of the invention, there is provided a basestation operable to share resources between at least two networkoperators, the base station comprising means for handing over aconnection associated with one of the at least two network operatorsbetween the base station and another base station based on a handovertrigger level associated with the one network operator, and means foradjusting handover trigger levels independently for each networkoperator.

The means for adjusting the handover trigger levels may be configured toadjust the handover trigger levels in dependence on a contribution toload on the base station for each network operator. The base station mayfurther comprise means for receiving information from a neighbouringbase station relating to a contribution to load on the neighbouring basestation for each network operator, wherein the means for adjusting thehandover trigger levels are further configured to adjust the handovertrigger levels in dependence on the contribution to load on theneighbouring base station for each network operator.

According to a further aspect of the invention, there is provided a basestation operable to share resources between at least two networkoperators, the base station comprising means for determining acontribution to load on the base station associated with a one of the atleast two network operators, and means for transmitting a request to afurther base station- to advance or delay handover of connectionsassociated with the one network operator from the further base stationto the base station based on the determined contribution to load.

The request may comprise a mobility change request message. The meansfor transmitting may be further configured to transmit a request todelay handover of connections associated with the one network operatorwhen it is determined that the load associated with the one networkprovider is above a threshold load level. The means for transmitting maybe further configured to transmit a request to advance handover ofconnections associated with the one network operator when it isdetermined that the load associated with the one network provider dropsbelow a threshold load level.

According to a further aspect of the invention, there is provided a basestation operable to share resources between at least two networkoperators, the base station comprising means for receiving a request toadvance or delay handover of connections associated with a one of thenetwork operators from the base station to a further base station, andmeans for adjusting one or more handover parameters associated with theone network operator based on the received request.

According to a further aspect of the invention, there is provided amobility management entity for use in a wireless communication networkconfigured to share core network capacity between at least two networkoperators, the mobility management entity comprising means forcommunicating for at least one of the network operators an availablecapacity at the mobility management entity for that network operator toat least one base station.

The means for communicating may be further configured to communicate theavailable capacity for each network operator to the at least one basestation in a Relative MME Capacity information element per PLMN idvalue.

According to a further aspect of the invention, there is provided a basestation for use in a wireless communication network configured to sharecore network capacity between at least two network operators, the basestation comprising means for receiving information relating to anavailable core network capacity associated with one of the networkoperators, and means for generating a new connection request associatedwith the one network operator based on the received information. The newconnection request is, of course, also generated based on a connectionrequest that is received from a mobile communication device.

The information relating to available core network capacity may compriseinformation relating to available capacity at a mobility managemententity shared by the at least two network operators.

The means for generating a new connection request for a particularnetwork operator may be further configured to select a mobilitymanagement entity from a plurality of mobility management entities toregister the new connection based on the available core network capacityfor the particular network operator associated with the mobilitymanagement entities.

According to a further aspect of the invention, there is provided amobility management entity for use in a wireless communication networkconfigured to share core network capacity between at least two networkoperators, wherein each network operator is assigned a proportion of acapacity of the mobility management entity, the mobility managemententity comprising means for determining if an overload condition hasbeen reached at the mobility management entity based on a load on themobility management entity, and means operable, in response todetermining an overload condition has been reached, to determine if aone of the network operators is exceeding the proportion of the capacityof the mobility management entity assigned to the one network operator,and if so to transmit a message to a base station indicating that newconnection requests associated with the one network operator should berejected or routed through another mobility management entity.

The message transmitted to the base station may comprise a MME OverloadStart message associated with the one network provider.

The mobility management may further comprise means operable to determinewhether the one network operator is no longer exceeding the proportionof the capacity assigned to that network operator and, if so, totransmit a further message to the base station indicating that newconnection requests associated with that network operator may beaccepted.

The further message may comprise a MME Overload Stop message associatedwith the one network provider.

According to a further aspect of the invention, there is provided a basestation for use in a wireless communication network configured to sharecore network capacity between at least two network operators, the basestation comprising means for receiving a message from a mobilitymanagement entity indicating that new connection requests associatedwith a one of the network operators should be rejected or routed throughanother mobility management entity, and means operable to reject newconnection requests associated with the one network operator or to routenew connection requests associated with the one network operator throughanother mobility management entity, in response to receiving themessage.

According to a further aspect of the invention, there is provided amethod of providing information for use in balancing a network loadbetween a base station and a neighbouring base station, wherein thecapacity of the base station is shared between at least two networkoperators, the method comprising determining a contribution to a load onthe base station associated with a one of the network operators, andproviding the determined contribution to the load on the base stationassociated with the one network operator to the neighbouring basestation for use in load balancing between the base stations.

According to a further aspect of the invention, there is provided amethod of balancing a load between a base station and a neighbouringbase station, wherein the capacity of the base station is shared betweenat least two network operators, the method comprising receiving amessage from the neighbouring base station, the message comprisinginformation relating to a contribution to a load on the neighbouringbase station associated with a one of the network operators, andperforming load balancing between the base station and the neighbouringbase station based on the received information.

Performing load balancing may further comprise performing load balancingfor connections associated with the one network operator based on thereceived information independently of any load balancing for connectionsassociated with any other of the network operators.

According to a further aspect of the invention, there is provided amethod of controlling handover at a base station shared between at leasttwo network operators, the method comprising adjusting handoverparameters used to control handover independently for each networkoperator sharing the base station, and handing over a connectionassociated with a one of the network operators between the base stationand a neighbouring base station based on a handover parameter associatedwith the one network operator.

According to a further aspect of the invention, there is provided amethod of load balancing between a base station and a neighbouring basestation, wherein the base station is shared between at least two networkoperators, the method comprising determining a contribution to load onthe base station associated with a one of the at least two networkoperators, and transmitting a request to the neighbouring base stationto advance or delay handover of connections associated with the onenetwork operator from the neighbouring base station to the base stationbased on the determined contribution to load.

According to a further aspect of the invention, there is provided amethod of load balancing between a base station and a neighbouring basestation, wherein the base station is shared between at least two networkoperators, the method comprising receiving a request to advance or delayhandover of connections associated with a one of the network operatorsfrom the base station to the neighbouring base station, and adjusting ahandover parameter associated with the one network operator based on thereceived request.

According to a further aspect of the invention, there is provided amethod comprising communicating, for at least one network operator, anavailable capacity at a mobility management entity for that networkoperator to at least one base station, wherein the capacity of themobility management entity is shared between at least two networkoperators.

According to a further aspect of the invention, there is provided amethod of generating a new connection request at a base station in awireless communication network configured to share core network capacitybetween at least two network operators, the method comprising receivinginformation relating to an available core network capacity associatedwith one of the network operators, and generating a new connectionrequest for a connection associated with the one network operator basedon the received information.

According to a further aspect of the invention, there is provided amethod of controlling admittance of new connection requests in awireless communication network configured to share core network capacitybetween at least two network operators, the method comprisingdetermining if an overload condition has been reached at a mobilitymanagement entity in the core network based on a load on the mobilitymanagement entity, and in response to determining that an overloadcondition has been reached, determining if a one of the networkoperators is exceeding a proportion of the capacity of the mobilemanagement entity assigned to the one network operator and, if so,transmitting a message to a base station indicating that new connectionrequests associated with the one network operator should not be routedthrough the mobility management entity.

According to a further aspect of the invention, there is provided amethod of controlling admittance of new connection requests in awireless communication network configured to share core network capacitybetween at least two network operators, the method comprising receivingat a base station a message indicating that new connection requestsassociated with a one of the network operators should be rejected, andrejecting new connection requests associated with the one networkoperator at the base station.

According to a further aspect of the invention, there is provided a basestation operable to share resources between at least two networkoperators, the base station comprising means for determining resourceusage of the base station associated with a one of the networkoperators, and means for managing the rate of incoming connectionrequests associated with the one network operator in dependence upon thedetermined resource usage.

In one embodiment, the determined resource usage is compared with athreshold value and the means for managing the rate of incomingconnection requests is arranged to reduce the rate of incomingconnection requests if the determined resource usage is above thethreshold. This may be achieved, for example by blocking one or more newconnection requests associated with the one network operator.

In a preferred embodiment, the base station may be further configured tobroadcast an indication that new connections associated with the onenetwork operator are blocked in response to the determined resourceusage being greater than the threshold, and/or to set an ac-Barringinformation element for the one network operator.

According to a further aspect of the invention, there is provided amethod of controlling the sharing of resources on a base station that isshared between at least two network operators, the method comprisingdetermining a contribution to a load on the base station associated witha one of the network operators, and blocking a new connection associatedwith the one network operator in response to the determined contributionto the load.

The invention provides, for all methods disclosed, correspondingcomputer programs or computer program products for execution oncorresponding equipment, the equipment itself (user equipment, nodes orcomponents thereof) and methods of updating the equipment.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the invention will now be described, by wayof example, with reference to the accompanying drawings in which:

FIG. 1 schematically illustrates a mobile telecommunication system of atype to which the invention is applicable;

FIG. 2 is a block diagram of a shared base station suitable for use inthe telecommunications networks of FIG. 1;

FIG. 3 schematically illustrates a mobile telecommunications systemincluding shared core network components; and

FIG. 4 is a block diagram of a shared mobility management entitysuitable for use in the telecommunications network of FIG. 3.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Overview

FIG. 1 schematically illustrates a mobile (cellular) telecommunicationsystem 1 in which two network operators, operators A and B, are able toprovide a mobile wireless communications service. Operator A has a corenetwork 2-A and operator B a core network 2-B. Each operator may alsoprovide one or more base stations or eNBs 4-A, 4-B as part of a radioaccess network (RAN) for allowing one or more mobile telephones, or userequipments, 8-A, 8-B to connect to their network and receive theservice. As will be understood by those skilled in the art, each basestation 4 operates one or more base station cells in whichcommunications can be made between the base station 4 and the mobiletelephones 8. For an eNB 4 associated with an operator, such as eNB 4-Aassociated with operator A, typically only mobile telephones 8-Aassociated with the relevant operator are able to connect and interactwith the wireless communication system via that eNB 4-A. Thus, onlymobile telephones 8-A configured to access services via service providerA are able to connect to the network via operator A's eNB 4-A without“roaming” away from their home network.

The telecommunications system 1 further includes shared eNB 6. OperatorsA and B agree to share in the capacity of the shared eNB 6 such thatboth a mobile telephone 8-A associated with operator A and a mobiletelephone 8-B associated with operator B are able to connect to thenetwork via the shared eNB 6 as though connecting through equipmentprovided by their own respective network operator. Thus, mobiletelephone 8-A may connect or handover to the shared eNB 6 as though theshared eNB 6 is an eNB associated with operator A, while mobiletelephone 8-B is able to connect to shared eNB 6 as though the sharedeNB 6 is an eNB associated with operator B.

Such an arrangement may be useful in areas of low population density, ormore generally areas having low bandwidth requirements, in order toallow both network operators to provide their service to that areawithout requiring both network operators to install their own RAN inthat area. In contrast, in areas with higher capacity requirements thenetwork operators may choose to install their own RANs rather thansharing capacity.

The shared base station (eNB) 6 can be connected to by mobile telephones8 associated with either of the network operators A or B that share thebase station 6, as though that base station 6 was a base stationbelonging to the respective network operator. It is noted that this isquite different to a mobile telephone associated with a first networkoperator forming a connection via the network of a different serviceprovider using the “roaming” mechanism.

In a roaming situation, the connection with the mobile telephone ismonitored and controlled by the visited network which then subsequentlybills the home network of the mobile telephone (generally atsignificantly increased cost). In contrast, the sharing of the radioaccess network, as in the current embodiment, is transparent to users ofthe network, and monitoring and control of connections is performedusing standard mechanisms as though the mobile telephone was connectedvia the network operator's own RAN.

Each operator's network is typically associated with a unique PLMN(Public Land Mobile Network) id value, which is used in the wirelesscommunication network to identify connections associated with aparticular network operator. Typically, the network operators willcontract to be provided with a certain proportion of the resourcesavailable at the shared base station. For security reasons, connectionsrelating to a particular network operator may be isolated fromconnections relating to other network operators based on the PLMN idvalue associated with each connection.

In order to monitor the use of network resources by each networkoperator, monitoring statistics are individually collected for networktraffic labelled with each PLMN id in use at the base station.Embodiments of the present invention are able to use the monitoringstatistics collected on a per PLMN id basis (i.e. on a per networkoperator basis) to allow network functions to be performed for eachnetwork operator at a shared base station independently of other networkoperators at the shared base station. For example, and as will bedescribed in more detail below, the collected statistics may be used toprovide load balancing between neighbouring base stations for eachnetwork operator.

Shared Base Station (eNB)

FIG. 2 is a block diagram illustrating the main components of the sharedbase station 6 shown in FIG. 1. As shown, the shared base station 6includes transceiver circuitry 31 which is operable to transmit signalsto and to receive signals from the mobile telephones 8 via one or moreantennae 33 and which is operable to transmit signals to and to receivesignals from the core networks 2 via an S1 network interface 35, andalso operable to communicate with other base stations using an X2interface 36. A controller 37 controls the operation of the transceivercircuitry 31 in accordance with software stored in memory 39. Thesoftware includes, among other things, an operating system 41, aperformance monitor module 43, a PLMN resource share limiter module 45,and a load balancing module 47. The performance monitor module 43 isconfigured to monitor performance counters on a per PLMN id basis, suchthat the performance counters are monitored separately for each networkoperator sharing the capacity of the base station 6. Similarly, the PLMNresource share limiter module 45 and the load balancing module 47 areconfigured to operate on a per PLMN id basis to ensure that servicelevel limits are enforced and to control load balancing for each networkoperator respectively.

Usage Control

To allow the performance of the network to be monitored, a range ofperformance measurement counters are provided by the performance monitormodule 43. In the case of a shared RAN in which the sharing operatorsmay contract to be provided with a certain service level, it becomesmore important to monitor the performance of the network in order toprove that the service level agreements are being satisfied. Inparticular, it is necessary to be able to monitor the usage of theshared network by each operator to ensure that network resources areshared fairly. As mentioned above, each operator's network willtypically be associated with a PLMN id value which can be used toidentify the operator associated with a connection. Thus, according toembodiments of the present invention, the performance measurementcounters are defined per PLMN id. For example, counters monitored in theperformance monitor module 43 for each PLMN id sharing the networkinclude:

-   -   Counters useful for the planning and network re-dimension on a        per PLMN id basis        -   including counters that count the number of RRC Connections            (Request, re-establishment) and E-RAB related procedures            (Setup, Release and modify).    -   Counters related to the resource utilization on a per PLMN id        basis        -   including measuring usage of physical resource blocks            (PRBs), usage of random access channels, throughput related            measurements (on IP layer as well as PDCP), active UE            measurements etc.    -   Counters useful for optimization activity on a per PLMN id basis        -   including counting the number of handover procedures taking            place (including intra frequency, inter frequency, inter RAT            handovers, etc.)

In this embodiment, the base station 6 monitors the resources used byeach network operator sharing the base station 6 against a service levelagreement for that service provider. This monitoring is performed by theperformance monitor module 43 as discussed above. The performancemonitor module 43 provides the monitored information to the PLMNresource share limiter module 45 which stores agreed usage limits foreach PLMN defining the proportion of the capacity at the base station 6assigned to each PLMN, and compares the resources used by each PLMN idwith the stored usage limits Thus, whenever a PLMN is determined to havereached a maximum level of contracted resource usage, the PLMN resourcelimiter module 45 will block further connection requests associated withthat PLMN id for example by setting a barring flag in a memory toindicate that connection requests associated with a certain PLMN idshould be refused. Instead of blocking all connection requests, the PLMNresource limiter module 45 may just block some new connection requests(for example 50%) associated with a PLMN id. In this way, the rate ofincoming connection requests is controlled independently for each PLMN.

According to some embodiments, the barring is achieved by setting anac-barring information flag (for example, the ac-BarringInfo IE or theac-BarringFactor IE or the ac-BarringTime IE) associated with the PLMNid in system information block 2 (SIB2). The SIB2 is then broadcastthroughout the cell area associated with the base station, including theinformation relating to the barring of new connections for each PLMN toindicate to any incoming mobile telephone 8 whether they may connect tothe base station based on their associated PLMN. Any incoming mobiletelephones will receive the broadcasted SIB2 and be able to determinewhether they will be allowed to connect to the base station 6 based ontheir associated PLMN id and the barring information per PLMN includedin the SIB2.

Load Balancing

In this embodiment, the shared base station 6 is able to communicatewith other neighbouring base stations (shared or non-shared) using theX2 interface 36. This allows certain network operations to be performedbetween base stations 6, reducing the load on core network entities suchas a mobility management entity. One of these network operationsincludes load balancing between neighbouring base stations 6, asprovided by the load balancing module 47.

In this embodiment, the load balancing modules 47 in the respective basestations take into account cell loading contributions for each PLMNsharing the capacity of the base station 6. To do this, the loadbalancing module 47 shares cell loading information (for each PLMN id)with neighbouring base stations 4, 6 so that they can perform loadbalancing operations in order to balance out the load from the differentPLMNs sharing the available resources of the shared base stations 6.This sharing may be performed in response to a specific request for theinformation from another base station (for example using ResourcesStatus Request/Report messages) or it may be reported to theneighbouring base stations from time to time or on a regular basis.Thus, even if a shared base station 6 is not at full capacity, the loadbalancing module 47 may still attempt to transfer some mobile telephoneconnections associated with one PLMN to another base station 4 or 6 orit may receive mobile telephone connections associated with a PLMN fromanother base station 6. Two example scenarios will now be described thatillustrate this “per PLMN” load balancing operation.

Scenario 1

In this scenario, a first base station cell has a network load of 50%and all of this load is being contributed by mobile telephoneconnections associated with a first network operator (PLMN 1), while noload is being placed on the first cell by mobile telephone connectionsassociated with a second network operator (PLMN 2). A second basestation cell has a network load of 80%, of which PLMN 1 contributes 30%to this load and PLMN 2 contributes the remaining 50%.

In this scenario, there is a clear imbalance of network resource usagefrom the two PLMNs. In order to correct this, an enhanced load balancingmethod is used in the load balancing module 47 that takes into accountthe contribution to the total load on each base station cell from eachPLMN. According to this enhanced method, the load balancing modules 47in the two base station cells exchange information relating to the loadcontribution associated with each PLMN id sharing the corresponding basestation cell. Thus the load balancing module 47 in the first basestation cell informs the load balancing module 47 in the second basestation cell that its network loading is 50% and that this is allassociated with PLMN 1. Similarly, the load balancing module 47 in thesecond base station cell informs the load balancing module 47 in thefirst base station cell that its network loading is 80%, of which PLMN 1contributes 30% and PLMN 2 contributes 50%.

As the second base station cell has the highest overall load, inaccordance with normal load balancing rules, the second base stationcell determines from the shared loading information that it shouldoffload some connections to the first base station cell. However, thesecond base station cell can see from the shared loading informationthat the capacity being used by PLMN 1 on the first base station cell isalready high, and therefore, the load balancing module 47 of the secondbase station cell transfers (wherever possible) connections associatedwith PLMN 2 (and not those associated with PLMN 1) to the first basestation cell. The load balancing module 47 in the second base stationcell can achieve this, for example, by reducing a handover trigger levelfor mobile telephones associated with PLMN 2 (whilst maintaining orincreasing the handover trigger level for mobile telephones associatedwith PLMN 1). As those skilled in the art will appreciate, the handovertrigger level depends on a number of different parameters (such ashysteresis values, frequency offsets, cell offsets, time-to-trigger andthe like) and any one or more of those parameters can be varied toeffect the desired change in the handover trigger level and/or timingfor mobile telephones associated with a PLMN.

In particular, during normal operation, mobile telephones 8 reportdetails of other base station cells in their vicinity to their currentlyserving base station cell. The mobile telephone 8 uses the handoverparameters mentioned above to determine trigger conditions for sendingthe Measurement Report (MR) and the base station initiates a handoverwhen it receives the MR. These reports include, among other things,signal strengths for signals received from those other base stationcells. When the mobile telephone 8 moves further away from the currentlyserving cell and closer to another cell, the serving cell can detectthis by comparing the signal measurement reports received from themobile telephone. If the measured signal strength associated withanother cell is greater than the handover trigger level, then thatmobile telephone may be handed over to that other cell (although otherreasons may actually prevent that from happening). Consequently, byassigning different handover trigger levels to the different PLMNs (ineach base station cell) and by lowering the trigger level used formobile telephones associated with PLMN 2 in the second base stationcell, the handover module 47 in the second base station cell canincrease the number of mobile telephones associated with PLMN 2 thatwill be transferred to the first base station cell. Simultaneously, theload balancing module 47 in the second base station cell may propose tothe load balancing module 47 in the first base station cell (or the loadbalancing module 47 in the first base station cell may determine byitself from the shared loading information) to delay handover ofconnections associated with PLMN 2 to the second cell (which can beachieved, for example, by increasing the handover trigger level it usesfor PLMN 2).

Thus, the load balancing modules 47 in the respective base station cellsact to try to equalize the loads on the two base stations and also totry to equalize the contributions made by each PLMN to the load on eachbase station.

Scenario 2

In a second scenario, the load on the first cell remains 50% entirelycontributed by the first network PLMN 1. However, in this case, the loadon the second base station is also 50% with the contributions to theload being split evenly between PLMN 1 and PLMN 2 with each contributing25% of the cell load.

As the two cells have the same overall loading of 50%, existing loadbalancing algorithms would not apply any load balancing actions betweenthe cells. However, taking into account the contribution to cell loadfrom each PLMN sharing the capacity, it is clear that there is animbalance in the usage of cell resources. Thus, having exchangedinformation on cell load per PLMN id, one or more of the following loadbalancing actions may be taken by the respective load balancing modules47 in the cells:

-   -   Connections associated with PLMN 1 can be offloaded from the        first base station cell to the second base station cell (i.e.        reduce the handover trigger level for PLMN 1 used in the first        base station cell)    -   The load balancing module 47 in the first base station cell can        signal the load balancing module 47 in the second base station        cell with a mobility change request to propose that the second        cell delays handover of connections associated with PLMN 1        towards the first cell    -   Handover of PLMN 2 connections from the first cell to the second        cell may be delayed (for example by increasing the handover        trigger level associated with PLMN 2 used by the load balancing        module 47 in the first cell)    -   The load balancing module 47 in the first base station cell may        signal the load balancing module 47 in the second base station        cell with a mobility change request to propose that the second        cell advances handover of PLMN 2 connections towards the first        cell.

Thus, in accordance with this embodiment, load balancing is provided ona per PLMN id basis for the shared base stations 6.

In addition, neighbouring base stations 6 preferably also inform eachother of any service level loading limits associated with each PLMN(i.e. an available capacity per PLMN id), so that any load balancingperformed does not contravene those limits. For example, in the secondscenario above if PLMN 1 has a defined loading limit of 25% on thesecond base station cell, then connections associated with PLMN 1 can'tbe offloaded from the first base station cell to the second base stationcell as this will contravene the service level agreement limits.Typically, these service level limits will be shared amongst the basestation cells during an X2 setup procedure or during a base stationconfiguration update.

Thus, the following changes in the load balancing module 47 may bepresent over prior art arrangements:

-   -   The X2 Setup/eNB Configuration Update message is modified to        include physical resource block usage/available capacity        Information Element (IE) per PLMN id in both Request and        Response messages.        -   Resources Status Request/Report messages used to communicate            information on base station resource status between base            stations are modified to provide information on a per PLMN            id granularity.    -   The Mobility Change Request procedures may be modified such that        the PLMN id is included in the Request to infoini the base        station cell that is less loaded to delay the handover of mobile        telephones of a certain PLMN (i.e. the PLMN which is using most        of the resources of the overloaded base station).        Shared MME

FIG. 3 schematically illustrates a communications system 3, according toa further embodiment of the invention, in which elements of the corenetwork 2 are also shared together with the radio access networkcomponents in a specific area. In this case, a number of shared basestations 6 are coupled to a shared mobility management entity (MME) 10.The shared base stations 6 shown in FIG. 3 are similar to thosedescribed above with respect to FIGS. 1 and 2. The shared MME 10 is thencoupled to the core network 2-A of operator A and the core network 2-Bof operator B, in order to be able to route connections made via theshared infrastructure to the correct network.

In the embodiment of FIG. 3, the different network operators asrepresented by the different PLMN ids, share the capacity of not justthe shared base stations, but also the mobility management entity 10. Inorder to facilitate this sharing of the MME 10, a mechanism is providedfor exchanging information relating to the capacity assigned to eachPLMN id between the shared mobility management entity 10 and one or moreof the shared base stations 6. As described in more detail below, thecapacity information per PLMN id can be used in selecting a MME whenforming a new connection in the network, and also to avoid overloadingof the shared MME by a subset of the network operators.

FIG. 4 is a block diagram illustrating the main components of the sharedMME 10 shown in FIG. 3. As shown, each shared MME 10 includestransceiver circuitry 51 which is operable to transmit signals to and toreceive signals from the shared base stations 6 via eNB interface 53 andwhich is operable to transmit signals to and to receive signals from thecore networks 2 via core network interface 55. A controller 57 controlsthe operation of the transceiver circuitry 51 in accordance withsoftware stored in memory 59. The software includes, among other things,an operating system 61, a relative MME capacity manager 63 and a MMEoverload function module 65. The relative MME capacity manager 63 storesinformation relating to the proportion of the network capacity providedby the MME that has been assigned to each PLMN, and is operable todistribute this information to the shared base stations 6 connected tothe MME 10 as discussed in greater detail below. The MME overloadfunction module 65 is activated when the load on the MME 10 is high (forexample above a threshold load) and in danger of affecting networkoperation, and is operable to instruct the shared base stations 6connected to the MME 10 to refuse new connections to avoid placingfurther load on the MME in dependence on the capacity assigned to eachPLMN.

When a mobile telephone attaches to the network, the connection isrouted to core network entities by the base station 6 based on capacityin the core network. In particular, the NAS Node Selection Functionallows selection of a mobility management entity (MME) from one of anumber of available MMEs in the core network with which to register themobile telephone. Currently, the available capacity for each MME isprovided to the base station 6 by the relative MME capacity manager 63using the relative MME capacity information element in a S1 setupresponse message. However, in the prior art systems, this informationrelates to the entire capacity of the MME and takes no account of acapacity assigned to one or more PLMNs sharing the MME.

However, in this embodiment, the capacity of the MME 10, and other partsof the core network, are shared between the different network operators(PLMNs) associated with different PLMN id values. Thus, in order tocorrectly route a new connection, the base station 6 needs to be awareof the MME capacity for each PLMN id sharing the capacity of the MME 10.

The relative MME capacity manager 63 of the shared MME 10 is configuredto provide a relative MME capacity information element for each PLMN idthat shares the capacity of the MME which informs the base station 6 ofthe available capacity for each PLMN at the MME 10. The base stations 6will receive similar information from all the MMEs and this allows thebase stations 6, to perform the NAS Node Selection Function to select anMME 10 to use when forming a new connection based the PLMN id of the newconnection and on the capacity per PLMN id at each of the different MMEs10. Thus, the base stations 6 are provided with information to select ashared MME with available capacity for a specific PLMN to route the newconnection associated with that PLMN.

Furthermore, if a specific PLMN approaches or exceeds its assignedcapacity at an MME 10, then it is important that that specific PLMN isnot able to use more capacity than has been assigned to it, at theexpense of the remaining PLMNs. However, if the capacity being used byother PLMNs at the MME 10 is relatively low, then the over use of theassigned capacity by this PLMN may be accepted.

The MME overload function 65 is operable to detect when the load on theMME approaches overload conditions, and to instruct connected basestations 6 to avoid placing any further load on that MME 10. In thepresent embodiment, in which different PLMNs have specific assignedcapacities, the MME overload function 65 takes into account the PLMN idassociated with network traffic at the MME. In particular, the MMEoverload function 65 indicates to the base station 6 that incomingtraffic associated with a particular PLMN should be rejected (or atleast not routed through that MME) when capacity available for that PLMNis exceeded.

For example, if two networks have contracted to share the capacity ofthe shared core network equally (i.e. each contracted a service level of50%) and the MME 10 reaches a high processing load triggering the MMEOverload function 65, the MME should determine how each network iscontributing to the load on the MME 10. If it determines that PLMN 1 isusing most of the resources in the MME 10, then the MME overloadfunction module 65 will indicate to the base station 6 that new requestsassociated with PLMN 1 should be rejected, while new requests associatedwith PLMN 2 may be admitted.

If the situation subsequently changes such that the two networks arecontributing equally to the overload on the MME 10, the MME overloadfunction 65 will indicate that new requests associated with either PLMN1 or PLMN 2 should be rejected. To facilitate this selective controlaccording to PLMN id, an information element comprising a list ofrequesting PLMNs is included in MME Overload Start and MME Overload Stopmessages sent by the MME 10 to connected base stations 6 in order toprovide the indications to reject new calls to the base stations.

In the above description, the shared base station 6, and the shared MME10 are described, for ease of understanding, as having a number ofdiscrete modules (such as the performance monitor module 43, the PLMNresource share limiter module 45, the load balancing module 47, MMEoverload function module 65 etc.). Whilst these modules may be providedin this way for certain applications, for example where an existingsystem has been modified to implement the invention, in otherapplications, for example in systems designed with the inventivefeatures in mind from the outset, these modules may be built into theoverall operating system or code and so these modules may not bediscernible as discrete entities.

Modifications and Alternatives

A number of detailed embodiments have been described above. As thoseskilled in the art will appreciate, a number of modifications andalternatives can be made to the above embodiments whilst stillbenefiting from the inventions embodied therein. By way of illustrationonly a number of these alternatives and modifications will now bedescribed.

While the above described embodiments have been limited to two networkoperators sharing capacity at a base station or in the core network, itwill be appreciated that three, four, or more network operators mayshare parts of the network, and that the described embodiments areequally applicable to networks shared by more than two operators.

In the above embodiment, a mobile telephone based telecommunicationssystem was described. As those skilled in the art will appreciate, thetechniques described in the present application can be employed in anycommunications system. In the general case, the base stations and themobile telephones can be considered as communications nodes or deviceswhich communicate with each other. Other communications nodes or devicesmay include access points and user devices such as, for example,personal digital assistants, laptop computers, web browsers, etc.

In the above embodiments, a number of software modules were described.As those skilled will appreciate, the software modules may be providedin compiled or un-compiled form and may be supplied to the base stationor the MME as a signal over a computer network, or on a recordingmedium. Further, the functionality performed by part or all of thissoftware may be performed using one or more dedicated hardware circuits.However, the use of software modules is preferred as it facilitates theupdating of the base station and the MME in order to update theirfunctionality. Similarly, although the above embodiments employedtransceiver circuitry, at least some of the functionality of thetransceiver circuitry can be performed by software.

The above embodiments have described a number of techniques in whichcontrol actions are performed based on a per PLMN basis. As thoseskilled in the art will appreciate, these different techniques can beperformed separately or together. For example the above described loadbalancing between base stations can be performed with or without theabove described techniques for avoiding overload at the MMEs.

In the above embodiments, a contribution to the load on a shared networkdevice associated with a particular PLMN was determined, and if the loadwas high, various different techniques were used to reduce the load. Asthose skilled in the art will appreciate, different techniques can beused to determine whether or not the load is high. One technique is tocompare the determined load with a threshold value representative of ahigh load. Alternatively, the determined load may be used to address alook up table that defines the appropriate action to take based on thedetermined load (which is analogous to comparing the load with a numberof different thresholds). In this case, each defined range of loads ofthe look up table would specify, for example, a different factor to beused to control acceptance of new connections associated with the PLMNor to control handover of existing connections associated with the PLMNto another base station etc.

Various other modifications will be apparent to those skilled in the artand will not be described in further detail here.

Introduction

RAN sharing deployment scenarios have already been popular since quitesome time and standard means to allow these scenarios have beenintroduced since Rel 5. However discussion on RAN sharingstandardization has been extended to accommodate new technology (LTE) aswell as new RAN sharing scenario (e.g. sharing of CBC).

In the past there has always been the assumption that the networkprovider would also be a service provider.

In this presentation NEC highlight a new use case of RAN Sharingscenario triggered by the business case where there is a clear splitbetween ownership and service providers. NEC also proposes a list ofchange that would be necessary for the standard specification toaccommodate this new scenario.

Discussion

Currently, following scenarios have been considered when specifying theRAN sharing feature:

-   -   Sharing only ran nodes        -   With common or split frequencies    -   Sharing EPC as well as RAN nodes        -   With common or split frequencies

In the above case, it is assumed that the service providers/operatorswill only share the resources.

The current standard mechanisms will also accommodate/cover the casewhere the Service provider/operator will integrate their businessprocesses (as T-Mobile and Orange have done in UK).

However, the current downturn economic situation, trends and drivershinting to potential opportunities, the difficulty for some operators tocapitalize has led to a new RAN scenario where the owner of the networkis not a service provider. In this case, each service provider will buya share of the network (formalized in a license agreement) based ontheir holding in the spectrum asset.

A use case of this scenario is what has happened in Russia where thecountry's major network operators—MTS, VimpelCom (Beeline), Megafon andRostelekom—will see Yota become their LTE network provider and guaranteethe roll out of its LTE network.

In such a scenario it is important that the standard has all the meansto:

-   -   Guarantee a fair usage of network resources according to their        share acquired/granted    -   Monitoring that the network is performing according to what was        sold them    -   Make sure that existing 3GPP features also accommodate this        scenario

In order to secure a fair usage of the network and allow network to bemonitored per PLMN id, it is important that the PM counters which arespecified in are defined per PLMN id. Here are some examples:

-   -   Counters useful for the planning and network re-dimension        -   These are counters related to RRC Connection (Request,            re-establishment) and E-RAB related procedure (Setup,            Release and modify)    -   Counters related to the resource utilization        -   These are counters related to the PRB usage, RACH usage,            throughput related measurements (on IP layer as well as            PDCP), active UE measurements    -   Counters useful for optimization activity        -   These are counters related to the handover procedure (Intra            frequency, inter frequency, inter RAT etc.)

In addition, NEC believes that some of the existing 3GPP features to beenhanced to accommodate this case as well (reasoning is given below).

NNSF (NAS Node Selection Function)

The NNSF, among other functions, foresees that the eNB routes UEsattaching to the network (i.e. GUMMEI not available) based on the EPCcapacity. The EPC capacity is informed by the MME to the eNB viaRelative MME Capacity IE in S1 SETUP RESPONSE. If the EPC capacity isshared among different service providers, the eNB should be aware of theMME Capacity per PLMN. Thus there should be a Relative MME Capacity IFper PLMN.

MME Overload

In case of GWCN, the MME Overload procedure needs to be enhanced so thatMME can indicate to the eNB that the traffic of a particular PLMN shouldbe rejected.

This for example would be the case when PLMN 1 and PLMN 2 have a 50-50split of the EPC and the MME reaches a high processing load and thustriggers the MME Overload procedure. In case the PLMN 1 is using most ofthe resources in MME, then MME should indicate to the eNB that userrequests belonging to PLMN 1 should be the ones to be rejected.

If the situation then changes such that both PLMN are equally using theEPC resources, then MME could indicate both PLMNs in the new MMEOverload message

In order to do that, a list of requesting PLMN id IE should be added inthe MME Overload Start and MME Overload Stop.

X2 Load Balancing

In order to understand why and how to enhance the load balancing relatedprocedure, two use cases have been highlighted below:

Scenario 1:

-   -   Cell 1: 50% loaded        -   PLMN1 contribute on the load with 50%        -   PLMN2 contribute on the load with 0%    -   Cell 2: 80% loaded        -   PLMN1 contribute on the load with 30%        -   PLMN2 contribute on the load with 50%

In such a scenario there is clear an unbalance usage of the resourcesfrom the 2 PLMNs. The enhanced Load Balancing should work as follow:

-   -   Cell 1 and cell 2 will exchange info on their load per PLMN id    -   Cell 2 will start load balancing i.e.:        -   Offload UEs of PLMN 2 in cell 2 to cell 1 (i.e. reduce HO            trigger). In this case load in cell 2 is reduced trough            offloading        -   Propose cell 1 to delay HO of PLMN 2 (i.e. increase ho            trigger). In this case cell 2 make sure that the HO of PLMN2            incoming UEs is delayed            Scenario 2:

Cell 1: 50% loaded

-   -   PLMN 1: contributes on cell load with 50%    -   PLMN 2: contributes on cell load with 0%

Cell 2

50% loaded

-   -   PLMN 1 contributes on cell load with 25%    -   PLMN 2 contributes on cell load with 25%

The 2 cells have same load and according to existing algorithm therewould be no Load balancing actions. However if the HO trigger is perPLMN, then LB actions could be:

-   -   Offloading PLMN1 UEs from cell 1 to cell 2 (i.e. reducing ho        trigger for PLMN 1 from cell 1 to cell 2)    -   Signal this via Mobility Change Request and propose cell 2 to        delay HO of PLMN 1 UEs towards cell 1 (i.e. increase HO trigger        from cell 2 to cell of PLMN 1 UEs)    -   Delay HO of PLMN 2 Ues from cell 1 to cell 2    -   Signal this via Mobility Change Request and propose cell 2 to        advance HO of PLMN 2 UEs towards cell 1 (i.e. reduce ho trigger        from cell 2 to cell 1 of PLMN 2 UEs)

To recap, in order to have a load balancing working per PLMN, therewould be a need for eNBs to know the capacity of each neighbors per PLMN(currently only the total cell BW is exchanged in X2 Setup). The eNBsshould be exchange the info on their resource status on a PLMNgranularity and finally the action (i.e. change of the HO trigger)should also be performed on a PLMN granularity. Accordingly, followingchanges would be needed:

-   -   Change in X2 Setup/eNB Configuration Update        -   Adding PRB usage/available capacity IE per PLMN id in both            Request and Response message    -   Change in Resources Status Request/Report        -   Adding requesting PLMN IF in Resource Status Request        -   Adding reporting PLMN IE in Resource Status Report    -   Change in Mobility Change Request procedure        -   Adding PLMN id to inform the node/cell less loaded to delay            the handover of UEs of a certain PLMN (i.e. the PLMN which            is using most of the resources of the overloaded eNB)            RRC Impacts

The eNB should be able to monitor the resources used by each PLMNagainst their granted ones. It should be possible to control the rate ofincoming connection requests independently for each PLMN. For example,when one PLMN has reached the maximum granted resources, eNB may blockfurther connection requests from UEs belonging to that PLMN. In order todo that, the ac-Barringlnfo IF in SIB 2 (system information block 2)should be set per PLMN. Using PLMN specific Access Class barringparameters, e.g. ac-BarringFactor or ac-BarringTime, the eNB can managethe rate of incoming connection requests independently for each PLMN.

CONCLUSION

In this paper has analysed a new RAN sharing scenario where there is aseparation between network ownership and service provider and hasproposed following changes in the standard in order to accommodate thisscenario:

-   -   New PM counters as listed in slide should be added in 32.425    -   S1 SETUP RESPONSE        -   Relative MME Capacity IF should be defined per PLMN    -   MME Overload Start        -   Adding Requesting PLMN id    -   MME Overload Stop        -   Adding Requesting PLMN id    -   X2 Setup Request        -   Adding PRB usage/available capacity IE per PLMN    -   X2 Setup Response        -   Adding PRB usage/available capacity IE per PLMN    -   eNB Configuration Request        -   Adding PRB usage/available capacity IE per PLMN    -   eNB Configuration Response        -   Adding PRB usage/avail able capacity IE per PLMN    -   Resources Status Request/Report        -   Adding requesting PLMN    -   Resources Status Request/Report        -   Adding reporting PLMN IE    -   Mobility Change Request        -   Adding HO trigger per PLMN id    -   RRC SystemInformationBlockType2:

ac-BarringInfo/ac-BarringForMO-Data should be defined per PLMN.

It is proposed to discuss the contribution and agree on the changespropose in R3-111992.

This application is based upon and claims the benefit of priority fromUnited Kingdom patent application No. 1108525.5, filed on May 20, 2011,the disclosure of which is incorporated herein in its entirety byreference.

The invention claimed is:
 1. A User Equipment that communicates with along term evolution, LTE base station, for an LTE Radio Access Network,shared by at least two operators, each operator being associated with arespective Public Land Mobile Network, PLMN, the User Equipmentcomprising: a transceiver circuit configured to receive a signal thatincludes access class barring (ac-barring) per PLMN information insystem information block 2 (SIB2), wherein the ac-barring per PLMNinformation provided in SIB2 comprises an ac-BarringInfo informationelement, IE, and an ac-Barring for mobile originating data(ac-BarringForMO-Data) IE, in association with information indicating aPLMN of one or more of the at least two operators; and a processorconfigured to consider access to a cell as barred based on the contentsof the ac-BarringInfo IE.
 2. A method for a User Equipment thatcommunicates with a long term evolution, LTE base station, for an LTERadio Access Network, shared by at least two operators, each operatorbeing associated with a respective Public Land Mobile Network, PLMN, themethod comprising: receiving a signal that includes access class barring(ac-barring) per PLMN information in system information block 2 (SIB2),wherein the ac-barring per PLMN information provided in the SIB2comprises an ac-BarringInfo information element, IE, and an ac-Barringfor mobile originating data (ac-BarringForMO-Data) IE, in associationwith information indicating a PLMN of one or more of the at least twooperators; and considering access to a cell as barred based on thecontents of the ac-BarringInfo IE.
 3. A long term evolution, LTE, basestation, for an LTE Radio Access Network that is shared by at least twooperators, each operator being associated with a respective Public LandMobile Network, PLMN, the base station comprising: a processorconfigured to generate a signal which includes access class barring(ac-barring) per PLMN information in system information block 2 (SIB2)wherein the ac-barring per PLMN information provided in SIB2 comprisesan ac-BarringInfo information element, IE, and an ac-Barring for mobileoriginating data (ac-BarringForMO-Data) IE, in association withinformation indicating a PLMN of one or more of the at least twooperators; and a transceiver circuit configured to broadcast the signal;wherein the contents ac-BarringInfo IE is configured to cause a UserEquipment to consider access to a cell as barred based on the contentsof the ac-BarringInfo IE.
 4. A method for a long term evolution, LTE,base station, for an LTE Radio Access Network which is shared by atleast two operators, each operator being associated with a respectivePublic Land Mobile Network, PLMN, the method comprising: generating asignal which includes access class barring (ac-barring) per PLMNinformation in system information block 2 (SIB2) wherein the ac-barringper PLMN information provided in SIB2 comprises an ac-BarringInfoinformation element, IE, and an ac-Barring for mobile originating data(ac-BarringForMO-Data) IE, in association with information indicating aPLMN of one or more of the at least two operators; and broadcasting thesignal, wherein the contents ac-BarringInfo IE is configured to cause aUser Equipment to consider access to a cell as barred based on thecontents of the ac-BarringInfo IE.